You are correct to assume that Adrian meant Buddhist monks. In June 1963, the Vietnamese monk Thích Quảng Đức burned himself in the middle of Saigon in protest of the persecution of Buddhists. This was followed by similar cases. Time expands:
The first and most famous moment of self-immolation as agitprop was that of Thich Quang Duc in 1963. Under the rule of Ngo Dinh Diem, South Vietnam largely advanced the agenda of the country's Catholic minority and discriminated against Buddhist monks. In one of the most dramatic instances of individual protest, Quang Duc doused himself in gasoline in the middle of a Saigon street and lit himself ablaze.
Afterward, four more monks and a nun set themselves ablaze protesting Diem before his regime finally fell in 1963. Rather suddenly, setting oneself on fire became a political act. As the American presence increased in Vietnam in the mid- to late 1960s, more and more monks committed self-immolation, including thirteen in one week.